1. Field of the Invention
The present invention relates to a drive unit for a conveyor with a driving motor, a hydrodynamic clutch and a supply system for operating material.
2. Description of the Related Art
It is known to use drive units with a hydrodynamic clutch in conveyors, in particular rubber belt conveyors, in order to realize a slow, jolt-free acceleration of the system, the damping of sudden increases of load, and the compensation of loads. This is to ensure in particular a wear-free transmission of power, a relieved run-up of the motor, and a smooth acceleration of extremely heavy masses. These advantages are particularly relevant for rubber belt conveyors as a result of the slippage occurring during the transmission of power. As a result of a respective operating mode of the drive unit, one can achieve an increase in the service life of the belt.
Particularly during applications in mining, it is common practice to operate these clutches with water as the operating material. In order to realize the discharge of heat in permanent operation, these clutches and the circulation of the operating material are designed in such a way that operating material is continuously discharged from the working circulation of the clutch. Thus, the heat occurring during the transmission of power is also continuously discharged.
Generally, two systems are applied:
1) The use of an open system; or PA1 2) The use of a closed system.
When using an open system, the clutches are fed from a fresh water line. When using a double clutch, i.e., a clutch with two circulations, the water control unit includes two water circulations also designated as operating circulations. For the purpose of start-up, the water circulations are filled with a large volume flow, whereas in permanent operation they are changed over to a reduced volume flow in the system. This flow is used for discharging the heat incurred during the transmission of the power.
As a result of the continuous passage of operating material, i.e., the continuous even supply and discharge of fresh water into and from the operating chamber, the overall system is simple, clearly structured and compact. A separate cooler for discharging the obtained slipping heat from the operating liquid is not required. However, the high consumption of water is disadvantageous, as fresh water must continuously be made available for passage through the clutch. Providing this water can be problematic depending on the respective application.
A second known possibility is to convey the operating material in a closed system with integrated cooling devices. For this purpose, the clutches are fed from a tank by way of connecting lines in the form of tubes. With respect to its level, the tank is arranged below the clutches. The operating liquid from the clutch, and from the operating chamber in particular, can thus flow back to the tank as a result of gravity. For the operation, however, a pump is required which conveys the operating material contained in the tank into the operating circulation of the clutch. It will be heated as a result of the transmission of power through the operating material. Spray-off nozzles are therefore provided on the outer circumference of the clutches through which there is a gradual escape of the operating material. The discharged heated operating material is collected in the operating material collection or clutch casing and reaches the tank from there by gravity.
Such a closed system is characterized in particular by a water-saving operating mode, but it requires an increased number of components and elements as well as an increased amount of space, particularly owing to the necessity of providing feed lines between the tank and the clutch and the difference in height between the operating chamber and the tank which is required to realize the return flow.